U.S. patent number 4,940,065 [Application Number 07/299,135] was granted by the patent office on 1990-07-10 for surgically implantable peripheral nerve electrode.
This patent grant is currently assigned to Regents of the University of California. Invention is credited to Curtis A. Gleason, Tom F. Lue, Richard A. Schmidt, Emil A. Tanagho.
United States Patent |
4,940,065 |
Tanagho , et al. |
July 10, 1990 |
Surgically implantable peripheral nerve electrode
Abstract
An electrode is adapted to be surgically implanted around a
nerve bundle to provide for the selective stimulation thereof. The
electrode comprises a biocompatible and dielectric carrier formable
from a flattened, opened position to a closed position around the
nerve bundle. In its opened position, the carrier exhibits a main
body portion extending in the direction of a longitudinal wrapping
axis of the carrier and flap portions extending transversely
outwardly from opposite ends of the main body portion and from the
axis. At least one electrode contact is secured on an inner surface
of the carrier and is welded to a wire lead, adapted for connection
to a receiver implanted on a patient. In carrying forth the method
steps for making the electrode, the carrier originally constitutes
a tube that is suitably cut to form the main body and flap portions
thereof. The electrode contact is then secured to an inner surface
of the carrier and welded to the wire lead.
Inventors: |
Tanagho; Emil A. (San Rafael,
CA), Schmidt; Richard A. (San Rafael, CA), Gleason;
Curtis A. (Palo Alto, CA), Lue; Tom F. (Millbrae,
CA) |
Assignee: |
Regents of the University of
California (Berkeley, CA)
|
Family
ID: |
23153450 |
Appl.
No.: |
07/299,135 |
Filed: |
January 23, 1989 |
Current U.S.
Class: |
607/118 |
Current CPC
Class: |
A61N
1/0556 (20130101) |
Current International
Class: |
A61N
1/05 (20060101); A61N 001/05 () |
Field of
Search: |
;128/784,785,642,419C |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Cohen; Lee S.
Government Interests
ACKNOWLEDGEMENT
This invention was made with Government support under Grant
Contract No. NS-18029 awarded by the DHHS. The Government has
certain rights in this invention.
Claims
I claim:
1. A peripheral nerve electrode adapted to be surgically implanted
around a nerve comprising
carrier means formable about a longitudinal wrapping axis thereof
from an opened position to a closed position encircling a nerve,
said carrier means composed of a biocompatible and dielectric
material and when in its opened position said carrier means having
a main body portion extending in the direction of said axis and
flap portions extending transversely outwardly from opposite ends
of said main body portion and from said axis and when in its closed
position said carrier means having opposed edges of opposite sides
of its main body and flap portions disposed in close abutting
relationship relative to each other to form a tube, and
electrode means secured on an inner surface of said carrier means
for selectively electrically stimulating said nerve when said
carrier means is in its closed position thereabout.
2. The nerve electrode of claim 1 wherein said carrier means
generally forms a cylindrical tube when in its closed position and
is composed of a polymeric material exhibiting a memory to
automatically assume its closed position when released from its
opened position.
3. The nerve electrode of claim 2 wherein said carrier means is
composed of a polymeric material having a physical character
comparable to milled and compounded rubber prior to vulcanization,
but containing organosilicon polymers.
4. The nerve electrode of claim 1 wherein said carrier means is
generally Z-shaped when in its opened and flattened position and
said main body portion is defined by a pair of opposite end edges
disposed transversely relative to said axis and parallel side edges
intersecting said end edges.
5. The nerve electrode of claim 4 wherein each said flap portion is
defined by a pair of parallel outer and inner side edges each
defining an acute angle relative to said axis and to a respective
one of the side edges of said main body portion.
6. The nerve electrode of claim 5 wherein said outer and inner side
edges intersect a respective one of the end edges and side edges of
said main body portion, respectively.
7. The nerve electrode of claim 6 wherein each said flap portion is
further defined by a distal edge intersecting the outer and inner
edges thereof and when said carrier means is in its closed position
each side edge of said main body portion being disposed to closely
abut a distal edge of a respective flap portion and the inner edges
of said flap portions being disposed to closely abut each other
with said carrier means generally assuming a cylindrical
configuration.
8. The nerve electrode of claim 1 wherein said electrode means
extends at least substantially circumferentially within said
carrier means and about said nerve when said nerve electrode is in
its closed position encircling said nerve.
9. The nerve electrode of claim 8 wherein said electrode means
comprises a wire or ribbon electrode contact extending transversely
across said main body portion, between outer side edges of said
flap portions.
10. The nerve electrode of claim 8 wherein said electrode means
comprises a plurality of wire or ribbon electrode contacts disposed
in spaced and parallel relationship relative to each other.
11. The nerve electrode of claim 10 wherein said electrode contacts
are disposed in parallel relationship relative to said axis.
12. The nerve electrode of claim 10 wherein said electrode contacts
are disposed transversely relative to said axis.
13. The nerve electrode of claim 8 wherein said electrode means
comprises a plurality of button-type electrode contacts.
14. The nerve electrode of claim 1 further comprising an electrical
lead means welded to said electrode means for connecting said
electrode means to a receiver implanted on a patient.
15. A peripheral nerve electrode adapted to be surgically implanted
around a nerve comprising
carrier means formable about a longitudinal wrapping axis thereof
from an opened position to a closed position encircling a nerve,
said carrier means composed of a biocompatible and dielectric
material and when in its opened position said carrier means having
a main body portion extending in the direction of said axis and
flap portions extending transversely outwardly from opposite ends
of said main body portion and from said axis, said carrier means
being generally Z-shaped when in its opened and flattened position
and said main body portion being defined by a pair of opposite end
edges disposed transversely relative to said axis and parallel side
edges intersecting said end edges, and
electrode means secured on an inner surface of said carrier means
for selectively electrically stimulating said nerve when said
carrier means is in its closed position thereabout.
Description
TECHNICAL FIELD
This invention relates generally to an electrode and method for
making the same and more particularly to a peripheral nerve
electrode adapted to be surgically implanted around a nerve
bundle.
BACKGROUND OF THE INVENTION
Electrical stimulation of a peripheral nerve (nerve bundle) is
required by certain electro-neuroprostheses to replace or augment
physiological body functions that have been compromised or rendered
ineffective by disease or trauma. For example, U.S. Pat. Nos.
4,585,005; 4,607,639; and 4,739,764, issued to inventors named
herein, disclose systems and methods designed for this purpose.
Peripheral nerve electrodes basically consist of a metallic
conducting material in the form of an electrode contact having an
attached lead and an insulating material that supports the
electrode contact.
The electrode contact is connected by its lead to a receiver,
implanted on a patient, whereby selective stimulation of the nerve
can be achieved in a conventional matter. The insulating material
provides a substrate or carrier that functions to hold the
electrode contact in a fixed position and further functions as a
dielectric to confine electrical current so that it does not affect
adjacent nerves, outside of the target area. The electrode contact
is normally composed of a platinum-irridium alloy that is innocuous
to living tissue, but yet delivers electrical current to the
contact at an acceptable level to activate (stimulate) the target
nerve. The insulating material composing the carrier is
biocompatible, such as a Silastic wrapping or sheeting capable of
providing the supporting and dielectric desiderata discussed
above.
Various geometric forms of electrode contacts have been proposed,
such as small circular or rectangular "buttons" and narrow foil or
small wire configurations that are stripped of insulation adjacent
to the point whereat a target nerve is positioned. The carrier is
normally formed as a "cuff" that encircles the nerve or as a
"spiral" that wraps around the nerve. The so-called cuff electrode
is placed around the nerve to form a continuous slit between
adjacent edges thereof. Sutures or staples are normally used to
attach the two adjacent edges of the cuff electrode together.
Application of these sutures or staples to the cuff electrode
requires a delicate surgical procedure after the cuff electrode is
placed on the nerve. Unless the separation line between the
opposing edges of the cuff electrode is properly sealed, the nerve
is susceptible to herniation upon the growth of post-surgical
tissue within the electrode lumen.
Another problem encountered with the use of the cuff electrode is
the relative rigidity of the carrier to which the electrode contact
is secured when the carrier is wrapped around a nerve. In
particular, when the carrier is formed into a cylinder around the
nerve, no space is left for accommodating tissue expansion when
tissue grows between the electrode contact and the carrier whereby
the nerve will assume a confined, constricted volume. Thus, in
order to prevent such constriction, the cuff electrode must be
formed to have a relatively larger diameter than the nerve to which
it is attached to allow for such tissue growth. The use of an
oversized cuff electrode obviously decreases the efficiency of the
stimulus/electrode system.
In the case of the spiral electrode, the composite outer diameter
thereof will normally increase to accommodate tissue growth.
However, since the spirals of the electrode that wrap around the
nerve are relatively narrow, the desired insulating properties of
the spiral electrode will be absent. Therefore, non-targeted
nerves, adjacent to the target nerve, will be stimulated by the
leakage of current, particularly when relatively high current
levels are used.
SUMMARY OF THE INVENTION
An object to this invention is to provide an improved peripheral
nerve electrode adapted for surgical implantation around a nerve
and a method for making such electrode.
The electrode comprises a carrier formable about a longitudinal
wrapping axis thereof from an opened position to a closed position,
encircling a nerve. The carrier is composed of a biocompatible and
dielectric material and, when in its opened position, the carrier
exhibits a main body portion extending in a direction of such axis
and flap portions extending transversely outwardly from opposite
ends of the main body portion and from the axis. One or more
electrode contacts are secured on an inner surface of the carrier
for selectively electrically stimulating the nerve when the carrier
is in its closed position thereabout.
In carrying forth the method steps of this invention, the electrode
is formed by first cutting a tube into the shape of the carrier and
then securing one or more electrode contacts thereto.
BRIEF DESCRIPTION OF THE DRAWINGS
Other objects and advantages of this invention will become apparent
from the following description of the accompanying drawings
wherein:
FIG. 1 is an isometric view of a plastic tube adapted to be formed
into a carrier or substrate for a peripheral nerve electrode of
this invention;
FIG. 2 is an isometric view illustrating the tube in its cut
condition to form the carrier;
FIG. 3 is an isometric view illustrating the carrier in its opened
and flattened condition with a wire electrode contact and a pair of
optional sutures secured thereon to form the peripheral nerve
electrode;
FIG. 4 illustrates the carrier and formed electrode in a partially
wrapped condition prior to its application to a nerve bundle;
FIG. 5 is a isometric view illustrating application of the carrier
and formed electrode to a nerve bundle and the further securance of
an electrical lead to the electrode contact thereof;
FIG. 6 is a top plan view of a first modification of the peripheral
nerve electrode with the electrode shown in its opened, flattened
condition;
FIG. 7 illustrates the FIG. 6 electrode in its closed position as
it would appear wrapped around a nerve bundle;
FIGS. 8 and 9 are views similar to FIGS. 6 and 7, respectively, but
illustrate a second modification of a peripheral nerve
electrode;
FIGS. 10 and 11 are views similar to FIGS. 6 and 7, respectively,
but illustrate a third modification of the peripheral nerve
electrode;
FIGS. 12 and 13 are views similar to FIGS. 6 and 7, respectively,
but illustrate a fourth modification of the peripheral nerve
electrode; and
FIGS. 14 and 15 are views similar to FIGS. 6 and 7, but illustrate
a fifth modification of the peripheral nerve electrode.
DESCRIPTION OF THE PREFERRED EMBODIMENT
FIGS. 1-5 sequentially illustrate a method for forming a peripheral
nerve electrode 20 and surgically implanting the electrode around a
nerve (nerve bundle) N. As shown in FIG. 5, the electrode comprises
a substrate or carrier 21 having an electrode contact 22 secured
therein for the purpose of selectively stimulating the nerve. The
electrode contact is welded at 23 to an electrical lead 24, adapted
for connection to a receiver (not shown) implanted on a patient in
a manner described in above referenced U.S. Pat. Nos. 4,585,005;
4,607,639; and 4,739,764.
In carrying forth the method steps for making electrode 20, a
cylindrical tube 21' shown in FIG. 1 is held in a suitable fixture
(not shown) and then formed with cuts 25 and further cuts to remove
a truncated portion at each end of the tube. The tube, forming
carrier 21, may be composed of any suitable biocompatible and
dielectric material commonly used for this purpose. For example,
the material may constitute Silastic which is a composition in
physical character comparable to milled and compounded rubber prior
to vulcanization, but containing organosilicon polymers.
Carriers or substrates fabricated from this material are
serviceable from -73.degree. to +160.degree. C., retain good
physical and dielectric properties when placed in a patient,
exhibit excellent resistance to compression set, weathering, and
corona. In addition, thermal conductivity of this material is high
and water absorption is low. When cut in tube form, as illustrated
in FIG. 1, the Silastic material will also exhibit physical
properties (flexibility, modulus of elasticity, etc.) whereby the
tube, when cut and flattened to its FIG. 3 condition will exhibit
sufficient "memory" to automatically reassume its cylindrical
configuration illustrated in FIG. 5.
Referring to FIG. 3, after the tube has been cut it is flattened
and preferably held by two or more clamps 26 for securance of
electrode contact 22 thereto. The electrode contact is preferably
composed of a standard platinum-irridium alloy that is innocuous to
living tissue, but yet delivers electrical current at an acceptable
level to stimulate a target nerve. The electrode contact may be
preformed into a standard ribbon or wire configuration or may
comprise a plurality of interconnected button electrode contacts,
described more fully hereinafter with reference to the embodiments
illustrated in FIGS. 12-15.
As shown in FIG. 3, flattened carrier 21 is formable above a
longitudinal wrapping axis X of the electrode from its illustrated
opened position to its closed position illustrated in FIG. 5,
encircling nerve N. In its opened position, main body portion 27 is
defined by a pair of opposite end edges 29 and parallel side edges
30 intersecting the end edges. Each flap portion 28 is defined by a
pair of parallel side edges 31 and 32 each defining an acute angle
"a" relative to a respective edge 30, shown as an approximating
60.degree..
Each outer side edge 32 and intersecting edge 29 are defined when a
respective truncated end portion of tube 21' is cut-off the tube.
Parallel distal edge 33 of flap portion 28 are preferably disposed
in parallel relationship relative to wrapping axis X of the
carrier.
When the carrier is thus viewed in plan, (flattened) it assumes a
general Z-shape to facilitate its compact wrapping about nerve N,
as illustrated in FIG. 5. When the carrier is so wrapped, each edge
30 of main body portion 27 will closely abut distal edge 33 of a
respective flap portion 28 whereas inner edges 31 will also be
placed in close abutting relationship relative to each other. Thus,
the carrier will again assume its substantial cylindrical
configuration illustrated in FIGS. 2 and 5 (with the truncated ends
of the cylinder removed). As discussed above, the plastic material
composing the carrier will preferably exhibit a "memory" whereby it
will automatically reassume its cylindrical configuration when
placed about the nerve.
Referring to FIG. 3, electrode contact 22 is shown in a form of a
ribbon or wire extending transversely across main body portion 27
of the carrier, between outer side edges 32 of the flap portions
thereof. As shown, the electrode contact further extends
transversely across wrapping axis X of the carrier and is disposed
at an acute angle "b", shown as approximating 35.degree..
Electrode contact 22 may be secured to the inner surface of carrier
21 by a suitable adhesive, such as the material composing the
carrier, or can remain unattached except for welds 23 (FIG. 5). A
Silastic could also be used to more firmly secure weld 23 and lead
24 to outside of the carrier, if so desired. In certain
applications, it may prove desirable to secure sutures 34 to
carrier 21 to aid in retaining the carrier and integrated electrode
on nerve N. One of the desired results in applying the herein
described electrodes to a nerve is that the electrical stimulation
be applied at least substantially circumferentially (360.degree.)
about all of the quadrants of the nerve.
FIGS. 6 and 7 illustrate a modification 20a of peripheral nerve
electrode 20 wherein identical numerals depict corresponding
components with numerals depicting modified components being
accompanying by an "a." A similar numbering system is used to
describe the embodiments illustrated in FIGS. 8-15.
FIGS. 6 and 7 illustrate a four-pair inline electrode configuration
wherein a plurality of wire or ribbon electrode contacts 22a are
secured in place on an inner surface of carrier 21 and are welded
externally of the carrier to leads 34 in the manner described
above. In the illustrated embodiment, electrode contacts 22a are
disposed in parallel relationship relative to each together and to
the longitudinal wrapping axis of the carrier.
FIGS. 8 and 9 illustrate a quadripolar electrode configuration 20b
wherein a plurality of wire or ribbon electrode contacts 22b are
disposed in parallel relationship relative to each other and
perpendicularly or transversely relative to wrapping axis X of
carrier 21b. The modified carrier exhibits a general hour glass
shape wherein a main body portion 27b is in the form of a web
interconnecting transversely extending flap portions 28b. Leads 34
are welded to the electrode contacts in the manner described
above.
FIGS. 10 and 11 illustrate a bipolar electrode configuration 20c
wherein a pair of longitudinally spaced electrode contacts 22c are
disposed in parallel relationship to each other and in
perpendicularly or transverse relationship relative to wrapping
axis X of carrier 21. Leads 34 are welded to the electrode contacts
in the manner described above.
FIGS. 12 and 13 illustrate a four-lead monopolar separated
electrode configuration 20d wherein a plurality of button-type
(circular or multi-sided) electrode contacts 22d are secured on the
inner surface of carrier 21. Additional leads 35 are disposed on
the inner surface of carrier 21 and interconnect the electrode
contacts with outer leads 34. It should be noted in FIG. 12 that
when electrode contacts 22d are secured to the inner surface of
carrier 21 that they are disposed in linear relationship relative
to each other and are further disposed transversely across the main
body portion of the carrier, i.e., similar to FIG. 3. When formed
into a general cylindrical shape, as illustrated in FIG. 13, the
electrode contacts will thus be spaced circumferentially
approximately 90.degree. from each adjacent electrode contact
whereby four quadrants of a nerve bundle will be stimulated.
FIGS. 14 and 15 illustrate a four-lead bipolar and paired electrode
configuration 20e comprising eight electrode contacts 22e. As
shown, internal leads 35 interconnect each mating pair of electrode
contacts together which are then connected to external leads
34.
* * * * *